Synthesis and properties of flavin ribofuranosides and flavin ribopyranosides

Ribose-containing coenzymes like flavin mononucleotide (FMN) can be conside red to be fossils of a prebiotic RNA world in which RNA encoded genetic inf ormation and catalyzed chemical reactions. To investigate the catalytic and base-pairing properties of FMN-containing oligonucleotides, the two cyclic flavin beta-D-ribosides 3 and 4 derived from riboflavin 2 were synthesized (Schemes 1 and 2). These are both constitutionally strongly related to the nucleobase uridine and should be able to participate as catalytically comp etent and informational nucleobases in DNA RNA, and p-RNA. Ribofuranaside 3 was too unstable to be isolated, but ribopyranoside 4 had the required sta bility, beta-D-configuration, and anti-conformation of the glycosidic bond.